Introduction: The ERS guidelines propose four pathways to confirm a diagnosis of asthma: i) FEV₁/FVC < 75% predicted AND bronchodilator reversibility (BDR) ? 12% AND ? 200ml, ii) fractional exhaled nitric oxide (FeNO) ? 50ppb, iii) peak exploratory flow variability (PEFv) ? 20%, and iv) methacholine bronchial challenge (BCT) PD₂₀ < 200ug.

Aim: Determine the sensitivity and specificity of the algorithm and of each pathway in RADicA, a prospective study of diagnostic methods for untreated people referred from primary care with symptoms of asthma.

Methods: Asthma diagnosis was made by a panel of asthma specialists using clinical history, physical examination, spirometry, BDR, PEFv, BCT, allergy testing, blood eosinophils, and response to 8 weeks inhaled corticosteroid treatment.

Results: Of 143 adults 118 had a definitive diagnostic outcome (75 female; mean (SD) age 36 (12) y, 70 (59%) had asthma). Performance of the algorithm and of each pathway is given in the table. Overall, 1 in 6 (17%) received a different diagnosis compared to the specialist panel, 13 (11%) with asthma were missed and 7 (6%) were wrongly diagnosed with asthma.

Conclusion: Widely available individual diagnostic tests for asthma proposed in the ERS guidelines (spirometry, BDR, PEFv and BCT) provide poor sensitivity but good specificity. Whilst the ERS algorithm provides a reasonable level of sensitivity and specificity, adjusting cut-off values for individual tests and/or adjusting the sequence may improve diagnostic performance.